NADH regeneration and NADPH regeneration

[pgaudet]

Continuing from #29050 (comment)

From @pgaudet – I am just wondering about NAD(P)H regeneration – some papers seem to mention this as a specific ‘purpose’ of some reactions, for example: https://pubmed.ncbi.nlm.nih.gov/7628449/

@rozaru :
NADH regeneration and NADPH regeneration
Def: A metabolic process that generates a pool of NAD(P)H by the reduction of NAD(P)+.

The problem with this term is that it usually corresponds to a 1 step reaction and is often embedded in other metabolic processes such as the oxidative branch of the pentose phosphate (1st reaction), conversion of pyruvate into lactate etc..

NAD(P)H regeneration in organelles is a bit more complicated as NADH and NADPH cannot cross the membrane and often involves more than 1 reaction.

In mitochondria, the regeneration is carried out by the glycerophosphate and malate/aspartate shuttles
In the peroxisome, depending on the species, it is carried out by the isocitrate/2-oxoglutarate shuttle (NADP) and malate-oxaloacetate shuttle (NAD).
In the section 2.4 of this reference they discuss the shuttles that “regenerate” the pools of NAD and NADP in the preoxisome.
There is the possibility to keep the term to group the shuttles but as the current definition stands curators are likely going to annotate any enzyme that involves NAD(P)H -> NAD(P) with this term when mentioned in the context of NAD(P)H regeneration.